Team Foundation Server (TFS) manages the entire application life-cycle using underlying process templates. TFS provides, off the shelf, three built-in process templates for managing the general execution of a project. There are also several community-developed templates available that can be integrated to TFS. If you need more than this, you can develop templates to handle specific aspects of the workflow that supports your application development process.

Topics covered in this article are

• Develop New Process Template
• Work Item Customization
  • Customization using WitAdmin Command
  • Process Editor
  • Custom Work Item
  • Custom Fields    
  • Custom Workflow
• Custom Work Item Control Development
  • Web Access Control
    • Create New Web Access Control – HTML Control
    • Create New Web Access Control – Based on TFS Core Control
  • Fallback mechanism        
  • Visual studio Control      
    • Create Custom Control  
    • Create wicc file
    • Package and Deploy      
    • Verify the new Custom Control
• Access Control  
  • Access Control at Field Level      
  • Access Control at Workflow level              

Please refer the article at

https://www.simple-talk.com/dotnet/visual-studio/customizing-team-foundation-server-2013/